Carbon black is used as a filler, pigment and/or reinforcing material in polymer composites, for example, in rubbers and in plastic masterbatches. Manufacturers require consistent quality and consistency in the carbon black. According to MaRS Market Intelligence Report Research in September 2011, worldwide carbon black consumption at that time was 9 million tonnes p.a., expected to reach 13 million by 2015. Average global growth will likely exceed 4% over the next five years. Ninety percent of the carbon black is used in the tire and rubber manufacturing sector.
According to a DATAMONITOR report on global tire and rubber publication in June 2011, the global tires and rubber market grew by 9.2% in 2010 to reach a value of $124.7 billion. $111 billion of that is in the tire market. In 2015, the global tires and rubber market is forecasted to have a value of $171.9 billion, an increase of 37.9% since 2010.
As the continuing accumulation of scrap tires has become a major global environmental hazard, there has been an increased focus on processes and methods for reclaiming the components of scrap rubber, including tire rubber. The materials reclaimed from rubbers are pyrolytic oil (pOIL), pyrolytic carbon black (pCB), non condensable gas and steel through pyrolysis process.
Scrap tires come from two sources: Post Consumer Scrap and Post Industrial Scrap, which is waste, defective parts or by-products. Scrap tires are composed of polymer composites, the thermal decomposition of the polymer composites (primarily natural rubber and styrene butadiene rubber) in an inert environment produces pyrolytic oil (pOIL), pyrolytic carbon black (pCB), non condensable gas and steel. Natural rubber coming from latex is mostly polymerised isoprene, thus pOIL can be considered as a partially sustainable oil. Presently the feedstock oil and fuel for making carbon black are all fossil fuel base.
The main feedstock for the production of virgin carbon black is fossil fuel. Although there are many trials in recycling of tire either by crumbing or by pyrolysis to reuse carbon black, these are not widely practiced due to quality issues. Some examples include the U.S. Pat. No. 7,329,329, U.S. Pat. No. 7,922,830, U.S. Pat. No. 6,221,329, U.S. Pat. No. 5,720,232, U.S. Pat. No. 6,835,861, U.S. Pat. No. 6,833,485, U.S. Pat. No. 5,037,628, US Patent Publication No. 2008/0286192, WO 99/08849, and WO 2006/119594.
Despite prior efforts to commercialize pyrolysis technology, it has not yet been achieved in an economically viable way. Although many pyrolysis projects have been proposed, patented, or built over the past decade, none have been commercially successful. Many of these processes are not truly continuous, but are, in at least some aspects or steps, limited to batch processing techniques. As such, they suffer from not being sufficiently scalable to be commercially viable. Others require excessive energy inputs to produce recycled/reclaimed material of sufficiently high quality to permit use in commercial products, with the result that they are not economical. In particular, the products of batch-type tire pyrolysis have limited marketability due to the low quality of their end products as compared to virgin materials. For instance, pyrolytic oil (pOIL) typically contains a mix of low volatile and heavy aromatic contents hydrocarbons. Moreover, with batch pyrolysis techniques, the consistency of the end products may vary with each run. As such, the resulting pOIL cannot be used for direct heating, or used as a direct feedstock in the petrol chemical industries. As a result, much of the pOIL, arising from existing pyrolysis processes, is used as recycled oil or used for blending in the fuel industry.
Polycyclic aromatic hydrocarbons (“PAHs”) are a large group of organic compounds having at least two fused aromatic rings. Examples of PAHs include naphthalene, anthracene, pyrene, benzofluoranthenes, benzopyrenes, etc. Many PAHs are known to be carcinogenic, mutagenic and/or teratogenic. The following Table 1 shows sixteen key PAHs and their boiling points.
TABLE 1PAH and Boiling PointPAHBoiling Point deg C.Anthracene342Acenaphthene96.2Acenaphthylene275benz(a)anthracene400benzo(a)pyrene360benzo(b)fluorantheneno databenzo(ghi)perylene550benzo(k)fluoranthene480Chrysene448dibenz(a,h)anthracene524Fluoranthene375Fluorine375indeno(1,2,3-cd)pyrene530Naphthalene218Phenanthrene340Pyrene404
PAHs are formed as a result of pyrolytic processes. Not surprisingly, PAHs are formed during the pyrolysis of organic materials such as coal and crude oil and during pyrolysis of rubber and other polymer composites. As a result, both virgin and reclaimed pyrolytic carbon blacks generally include relatively high levels of PAHs. Given the negative health and environmental effects from PAHs, there is increased public and regulatory pressure to reduce PAH levels in carbon blacks, particularly carbon blacks destined for use in the manufacture of plastic materials and articles intended to come into contact with foodstuffs.
A need remains for a pCB that can be reliably incorporated in commercial products, such as polymer composites, as a total or partial replacement for the virgin carbon black presently used in these products. Further, there remains a need for a pCB that has low PAH levels and that can be reliably incorporated in commercial products.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.